Atactic Polypropylene Research Articles

Extensional rheology of highly-entangled α-olefin molecular bottlebrushes

The transient uniaxial extensional response of a series of ultrahigh molecular weight poly(α-olefins) (PαO) with densely grafted bottlebrush architectures was measured as a function of side chain length, N sc. The PαO bottlebrushes studied here have N sc values ranging from 6 carbons [poly(1-octene)] to 16 carbons [poly(1-octadecene)] (POD). To understand the effect of bottlebrush architecture on the nonlinear response, a linear polyolefin (polypropylene), with N sc = 1, was included in this study. All the PαO bottlebrushes show strong extensional strain hardening (SH) at Weissenberg numbers, W i R, greater than 1. Strain-hardening ratios, S H R = η E + ( t ) / η E , LVE +, show increasing dependence on the rate of extension, described by power laws, with exponents dependent on the N s c values. Moreover, the maximum SHR values, S H R max, are increasing function of the side chain length, reaching values more than one order of magnitude larger for the POD, compared to atactic polypropylene (aPP, e.g., at W i R ∼ 200, S H R max = 3.5 and 75 for PP and POD, respectively). Another remarkable feature of these PαO bottlebrushes is their large extensibility, which is also an increasing function of both the extension rate and the side chain length. For instance, the maximum macroscopic stretch ratio values (before breakup), λ max, reach values of ∼400 (for POD), which is more than an order of magnitude larger than that for aPP ( λ max ∼ 25 ). A mechanism to explain the strong SH and stretchability in the PαO bottlebrushes, based on flow-induced side chain reorientation and interdigitation, is discussed.

Dielectric relaxation and trap-modulated DC breakdown of polypropylene blend insulation

This work focuses on the dielectric relaxation of isotactic polypropylene (iPP), syndiotactic polypropylene (sPP) and atactic polypropylene (aPP) blended insulation. The relationship between dielectric relaxation and trap characteristics, as well as their effects on the breakdown properties of polypropylene insulation are investigated. Frequency domain spectroscopy (FDS) is employed to characterize the dielectric relaxation of PP blends at 50, 70 and 90 °C. Isothermal surface potential decay (ISPD) measurements are carried out to obtain the trap characteristics, and the dc breakdown strength is tested; thus, the mechanisms of trap characteristics on the dielectric relaxation and breakdown performance are analysed. The dielectric relaxation processes α and δ of PP blends can be attributed to segmental motions and carrier hopping, respectively. The α relaxation strength (Δεα) decreases with the addition of sPP, since the intermolecular interaction factor (g) between PP molecules is weakened. The activation energy of δ relaxation is proportional to the shallow trap level, since the increased shallow trap level can pose higher potential barriers for carrier hopping. The higher crystallinity of PP blends can induce more deep traps in the boundaries of spherulites, and it can reduce the number of shallow traps that are mainly distributed in amorphous regions. The increased deep trap density serves a function to reduce the mean free path of charges and restrain impact ionization, resulting in an enhancement in the breakdown field.

Structuraland Mechanical Properties of Polymer—Paraffin Composites

The deformation—strength (strength and plasticity) and dilatometric properties (contraction or volume shrinkage) of binary composites of food paraffin P-1 and the polymers low-pressure polyethylene, polyethylene waxes, atactic polypropylene, and copolymers of ethylene and vinylacetate are investigated. The structural and mechanical properties of the polymer—paraffin composites are plotted as functions of composition. The dependences of these properties on the content of modifying component in the P-1 composites are compared.

Industrial waste origin succinic anhydride‐grafted atactic polypropylene as compatibilizer of full range polypropylene/polyamide 6 blends as revealed by dynamic mechanical analysis at the polypropylene glass transition

This work deals with a dynamic mechanical analysis (DMA) study on the effect of a novel interfacial agent containing maleated grafts on an industrial waste origin atactic polypropylene. This contains 3% of bridge‐, backbone‐, and terminal‐grafted succinic anhydride groups (aPP‐SA/SA). By considering a polymer blend as a special case of composite where the dispersed phase is mobile, it is assumed that both the amounts of polyamide 6 (PA6) and the interfacial agent (aPP‐SA/SA) cause changes in the glass transition temperature of the polypropylene phase in the blend. In this work, we have used DMA parameters to evidence the real interfacial modifications caused by the presence of aPP‐SA/SA in the isotactic polypropylene (iPP)/PA6 system at the iPP glass transition temperature on the basis that this is an unfavorable scenario for the action of aPP‐SA/SA. Since each component of the blend is interacting with each other, and to include the influence of the dispersed phase, it is possible to use a Box–Wilson experimental design model by resembling the so‐called “agent based models” to obtain algorithms forecasting the dynamic mechanical parameters (storage, E’, and loss moduli, E”) at the glass transition of iPP, in all the composition range of whatever iPP/PA6/aPP‐SA/SA‐modified blend. POLYM. ENG. SCI., 59:2458–2466, 2019. © 2019 Society of Plastics Engineers

New Test Method for Measuring Reflective Cracking in Hot-Mix Asphalt Overlay Pavements

Reflective cracking is a common distress in hot-mix asphalt (HMA) overlay. A test method that can provide comprehensive information about reflective cracking is thus needed. In this study, an apparatus named Joint Motion Simulation System (JMSS) was developed, which consists of two hydraulic servo-systems and a temperature chamber. A newly developed reflective cracking test method (NRCTM) based on JMSS was proposed, which is applicable for airport pavement. This method considers the influences of both traffic and thermal loads under controlled temperature conditions. Laboratory tests were conducted to verify both repeatability and sensitivity of the NRCTM. The tests results revealed a coefficient of variation that was lower than 13%, indicating that the NRCTM exhibited satisfactory repeatability. In addition, the method was sensitive to four factors: test temperature, combination of loads, compaction of specimen, and type of mixture. Moreover, three types of interlayer structures were evaluated with the NRCTM: geotextile, stress-absorbing layers, and atactic polypropylene modified linoleum. The geotextile performed better than the other two interlayer systems. Thus, the NRCTM can be used for measuring the reflective cracking in HMA overlay with acceptable repeatability and sensitivity.

Optically Transparent Functional Polyolefin Elastomer with Excellent Mechanical and Thermal Properties.

Synthesis of a variety of optically transparent polyolefin elastomers consisting of hard segment of polynorbornene and several kinds of soft segments such as atactic polypropylene, poly(ethylene-co-propylene), and poly(ethylene-co-1-hexene) was achieved. The block copolymers exhibited excellent toughness and thermal property with efficient elastic recovery. Most importantly, the introduction of hydroxyl group into polynorbornene segment not only modulated surface property of block copolymers, but also improved their mechanical properties.

Influence of the Environment on the Phase II - I Transformation of Isotactic Polybutene - 1

The phase II to I transformation process of isotactic polybutene – 1 (iPB-1) is influenced by the environment besides the usual physical factors. The phase II → I transformation rate depends, first of all, on the segmental mobility of the polymer chains. Environmental substances which are good solvents of iPB-1 increased the phase transformation rate at room temperature. Other substances, such as air, water, some acids or blends with atactic polypropylene, decreased the transformation rate in comparison with a sample exposed to a phosphorus pentoxide desiccant environment. The environmental effects also influence several other structural characteristics, such as sample crystallinity and crystallite size.

Sealing mastics for road surfacing in Siberian regions

This paper provides the results of the studies of polymer-bitumen sealing compounds for sealing seams and cracks in asphalt con-crete road. The polymers used were waste from Krasnoyarsk factories (rubber-fabric and butyl-rubber crumbs) and Tomsk factories (polyethylene waste and atactic polypropylene). Here we formulate the basic require-ments for sealing compounds applied in the Siberian regions. An experi-ment has been carried out with the use of the planning method, we pre-pared the compounds and determined their basic properties, as well as plot-ted the isolines of the compounds’ properties depending on the proportion-ing of mineral powder and polymer waste. Based on the analysis of the iso-lines and comparing the properties with the requirements, we selected the optimal compositions of the prepared sealing compounds and defined their core indicators. As a result of the research, the mastic based on butyl-rubber crumbs was chosen as the one meeting all the requirements by all the indicators. This paper reflects the results of the test surveys on pouring cracks in the road surface of Krasnoyarsk. The developed sealing com-pound has been adopted in production on the roads of Krasnoyarsk Territo-ry.

Enhancing stereoselectivity of propylene polymerization with MgCl2-supported Ziegler-Natta catalysts by electron donor: Strong effects of titanium dispersion state

Propylene polymerization with two TiCl4/MgCl2 catalysts (Cat-1: Ti 0.1%; Cat-2: Ti 1.0%) showed different responses to (cyclo-C5H9)2Si(OCH3)2 (De) addition. Cat-1 was deactivated more than Cat-2 by De. Amount of three groups of active centers producing atactic, medium isotactic and isotactic polypropylene chains were all reduced by De addition, but those of Cat-1 were reduced more. Reactivity of the isospecific active centers (kpi) was enhanced by De, but kpi of Cat-2 was changed more sensitively than Cat-1. The lower stereoselectivity of Cat-1 than Cat-2 are attributable to weaker De adsorption on its surface Mg, and the more sparsely dispersed Ti species on Cat-1 is responsible for weak De adsorption.

Prediction of χ Parameter of Polymer Blends by Combining Molecular Simulations and Integral Equation Theory.

A combination of molecular simulations and integral equation theory is applied to predict the χ parameter for polymer blends. The inter- and intramolecular structures of the polymer blends are obtained from molecular dynamics (MD) simulations with atomistic models, which, in turn, are used to calculate the χ parameter using the integral equation theory (χI). This approach was employed to determine the temperature and concentration dependence of χI in the binary blends of atactic polypropylene (aPP)-head-to-head polypropylene (hhPP) and polyethylene (PE)-isotactic polypropylene (iPP), respectively. The χ parameter calculated from this approach (χI) is compared with the χ parameter estimated in the literature from phase equilibrium simulation data for aPP-hhPP blends. In the case of PE-iPP blends, χI is compared with the χ parameter obtained from fitting the structure factor to the random phase approximation. Our approach for calculating χ does not require any fitting, and the only input required for the approach is the radial distribution function which can be calculated from MD simulations. Thus, using this approach in conjunction with atomistic models provides a general methodology for predicting χ parameter of polymeric systems of any chemistry.

Injection Molded Segregated Carbon Nanotube/Polypropylene Composite for Efficient Electromagnetic Interference Shielding

Constructing segregated structure in conductive polymer composite (CPC) is effective to achieve high electromagnetic interference shielding effectiveness (EMI SE) at low filler loading. Nevertheless, the present segregated CPCs were only fabricated via the compression molding technique, which limits their practical application. In this work, the injection molding technique was utilized for the first time to develop a carbon nanotube (CNT)/isotactic polypropylene (iPP)/atactic polypropylene (aPP) composite with typical segregated structure. The injection molded segregated CNT/PP composite exhibits an excellent EMI SE of 43.1 dB, which is 67% higher than the CNT/PP composite with randomly distributed CNTs, at the same CNT loading of 5.0 wt %. Such EMI SE is also comparable to the value for segregated CNT/PP composites prepared by compression molding. Our work provides a promising strategy to develop segregated CPCs via an efficient injection molding technique, in comparison to the compression molding technique.

Facile Preparation of a Novel Transparent Composite Film Based on Bacterial Cellulose and Atactic Polypropylene

Abstract A transparent bacterial cellulose/atactic polypropylene (BC/at-PP) composite film was prepared by a very facile “sandwich” hot-press method. The resulting BC/at-PP composite film exhibited good transparency, hydrophobicity, and significantly enhanced mechanical properties, indicating its tremendous potential as transparent film for food packaging and optoelectronics applications.

Interfacial Properties and Hopping Diffusion of Small Nanoparticle in Polymer/Nanoparticle Composite with Attractive Interaction on Side Group.

The diffusion dynamics of fullerene (C) in unentangled linear atactic polystyrene (PS) and polypropylene (PP) melts and the structure and dynamic properties of polymers in interface area are investigated by performing all-atom molecular dynamics simulations. The comparison of the results in two systems emphasises the influence of local interactions exerted by polymer side group on the diffusion dynamics of the nanoparticle. In the normal diffusive regime at long time scales, the displacement distribution function (DDF) follows a Gaussian distribution in PP system, indicating a normal diffusion of C. However, we observe multiple peaks in the DDF curve for C diffusing in PS melt, which indicates a diffusion mechanism of hopping of C. The attractive interaction between C and phenyl ring side groups are found to be responsible for the observed hopping diffusion. In addition, we find that the C is dynamically coupled with a subsection of a tetramer on PS chain, which has a similar size with C. The phenyl ring on PS chain backbone tends to have a parallel configuration in the vicinity of C surface, therefore neighbouring phenyl rings can form chelation effect on the C surface. Consequently, the rotational dynamics of phenyl ring and the translational diffusion of styrene monomers are found to be slowed down in this interface area. We hope our results can be helpful for understanding of the influence of the local interactions on the nanoparticle diffusion dynamics and interfacial properties in polymer/nanoparticle composites.

Mechanism of internal and external electron donor effects on propylene polymerization with MgCl2‐supported Ziegler–Natta catalyst: New evidences based on active center counting

ABSTRACTTwo TiCl4/Di/MgCl2 type supported Ziegler–Natta catalysts were prepared by loading dibutylphthalate or dicyclopentyldimethoxysilane (DCPDMS) (internal donor, Di) and TiCl4 on activated δ‐MgCl2 in sequence, and a blank catalyst was prepared by loading TiCl4 on the same δ‐MgCl2 without adding Di. These catalysts have similar specific surface area and pore size distribution, thus form a suitable base for comparative studies. Propylene polymerization with the catalysts was conducted in n‐heptane slurry using triethylaluminum (TEA) as cocatalyst, and the effects of Di as well as De (external donor, in this work it was DCPDMS) on the number of active centers, the distribution of active centers among three polypropylene (PP) fractions (isotactic, medium isotactic, and atactic PP chains), and chain propagation rate constants of the PP fractions were studied by counting the number of active centers in the PP fractions using a method based on selective quench‐labeling of the propagation chains by 2‐thiophenecarbonyl chloride. When De was not added in the polymerization, introducing a phthalate type Di in the catalyst evidently changed the active center distribution by enhancing the proportion of active centers producing isotactic PP (iPP) ( ), but scarcely changed reactivities of the three groups of active centers forming the three fractions. When the De was added in the polymerization system with TiCl4/phthalate/MgCl2 catalyst, further shifting of active center distribution in favor of took place, meanwhile reactivities of the three groups of active centers also remarkably changed in favor of . Mutual effects of these changes led to overwhelming dominance of iPP production in the TiCl4/Di/MgCl2–TEA/De system (Di = phthalate, De = alkoxysilane). In contrast, though using alkoxysilane as Di also caused shifting of active center distribution in favor of when De was not added, addition of alkoxysilane De caused reverse shifting of active center distribution in favor of those producing PP of lower stereoregularity. This unfavorable change largely counteracted the reactivity changes in favor of caused by the De, rendering the catalytic system rather poor isospecificity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46605.

Graphite nanosheets - polypropylene composites from in toluene delaminated graphite using atactic polypropylene as dispersant

Composites of polypropylene (PP) and graphite nanosheets (GN) are prepared by melt blending PP with a master batch of GN suspended in atactic polypropylene (Mw = 129.000 g/mol). aPP/GN master batches were obtained by wet ball-milling graphite in toluene using the aPP as dispersant. The procedure gives single flakes of GN with crystallite out-of-plane thickness as low as 17.7 nm. PP/aPP/GN composites were obtained with finely dispersed GN, predominantly as single nanosheets from master batches containing aPP dispersant and graphite. Crystallization of the iPP in the composites is facilitated by the presence of aPP and GN. PP spherulites are formed as the graphitic fillers act as strong nucleating agents: the dimensionality of the crystal growth (n = 2-3) and the crystallinity increases with increasing filler content in isothermal and non-isothermal crystallizations. The yield strength of the composites can be enhanced up to 20% by the presence of GN; the presence of aPP counteracts a decrease in elongation at break. Composites prepared from parent graphite or GN without aPP show larger aggregates of nanosheets in the composites.

TECHNOLOGICAL ASPECTS OF PRODUCTION AND RESEARCH OF POLYMERS COMPOSITE MATERIALS WITH INCREASED STRENGTH

The work is devoted to the search for new effective modifying additives that allow to purposefully regulate the technological properties of rubber compounds and physical-mechanical properties of rubbers based on combinations of non-polar rubbers and at the same time being cheaper and more affordable than traditional products, in particular, with resorcinol-urotropin complex (modifier RU -1). It was proposed to use as a modifier of frame rubbers based on a combination of isoprene (SKI-3) and butadiene-styrene (SCS-30ARKM-15) rubbers, chlorinated atactic polypropylene (CHAPP). It is shown that when the RU-1 modifier is replaced with this compound, the conditional stresses and tensile strength, tearing resistance, rebound elasticity, fatigue resistance in the regime of constant deformation amplitude, heat resistance, resistance to thermal aging of rubbers, as well as the strength of rubber bonding with rubber Textile cord, including at elevated temperatures are observed. Comparison of the CHAPP for the effectiveness of the action in the carcass gum with the previously proposed oligoefirmetacrylate epichlorhydrine, from the point of view of the provided complex of properties, showed the advantage of chlorinated atactic polypropylene for a number of priority indicators. From the comparative analysis of the modifying activity of chlorinated atactic polypropylene and oligoether methacrylate epichlorohydrin, it follows that the vulcanizates of rubber compounds containing instead of RU-1 chlorinated atactic polypropylene CHAPP are characterized by more improved parameters of hardness in TM-2, elasticity by rebound, the strength of the rubber-cord connection. It is also revealed that the main advantage of the proposed modifier is the low cost of the modifier used, as well as the use of secondary raw materials for its production.Forcitation:Mustafayeva R.E. Technological aspects of production and research of polymers composite materials with increased strength. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 82-86

Adhesion properties of atactic polypropylene/acrylate blend copolymer and its adhesion mechanism for untreated polypropylene materials

The adhesion and coating of polypropylene (PP) materials usually requires pre-processing, or the use of modified chlorinated polypropylene (CPP) as an adhesive, which is often synthesized in a benzene solution. Here a feasible method was achieved to modify atactic polypropylene (APP) to obtain an adhesive for polypropylene. Through “grafting from”, acrylate monomers were successfully grafted onto atactic polypropylene to obtain a blend copolymer in a butyl acetate solution. The adhesive presented excellent adhesion to polypropylene. A maximum peel strength of 12.9N/m was achieved. A mechanism to account for this enhanced adhesion between the blend copolymer and PP was proposed. In addition to a van der Waals force contribution, it was concluded that the promotion of adhesion included the contributions from diffusion and entanglement together with crystallization.

Chemical modification of road asphalts by atactic polypropylene

The results of experiments on chemical modification of viscous road asphalts with atactic polypropylene (APP) obtained by polymerization over a titanium–magnesium catalyst are presented. It has been shown that the preparation of an asphalt–polymer binder (APB) in an asphalt melt at 140°С is accompanied by the thermo-oxidative degradation of APP. The reaction scheme for chemical interaction of polyconjugated bitumen compounds with oxidized APP is presented. The APB materials with APP feature improved resistance to thermo-oxidative degradation and aging, high adhesion to mineral fillers, hardness, and heat resistance. A single-step technology for production of APB has been developed. The road concrete mixes with APP possess the lower water saturation and swelling in water, enhanced strength at 20 and 50°С, a low coefficient of heat sensitivity and enhanced crack resistance. The possibility of preparation of stone mastic asphalt (SMA) without admixture of specialty stabilizing fibrous additives has been experimentally proven.

A DMA study of the interfacial changes on injection‐molded iPP/mica composites modified by a p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene

ABSTRACTPresent work concerns to the study of the dynamic mechanical and thermal responses of selected polypropylene (iPP)/mica composites with a modified interface from the matrix side by using a p‐phenylen‐bis‐maleamic acid grafted atactic polypropylene, coming from a byproduct of industrial polymerization reactors. Thus, the study is mainly focused on the 75/25 iPP/mica ratio since it was identified in previous works as providing the maximum inter mica particle distance to assure they should participate in the overall process of dissipation of the mechanical energy supplied to the composites. Hence, the present dynamic mechanical analysis discussion tries to correlate the damping responses of the injection‐molded composites with those previously obtained but over compression molded composites as the basis of further studies all along the compositional iPP/mica map. Therefore, the latter let us, on the one hand, to follow how the main values of the different dynamic mechanical analysis parameters vary because of the interfacial modifier presence, and on the other, to develop a robust correlation between them and the corresponding macroscopic mechanical parameters. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45366.

Preliminary dynamic‐mechanical analysis of polypropylene/short carbon fibers composites modified by a succinic anhydride‐grafted atactic polypropylene

The present work checks on the efficiency of a grafted atactic polypropylene, with a high level of succinic anhydride‐grafted groups, as an interfacial modifier in Polypropylene/Short Carbon Fiber composites (iPP/SCF) by mean of Dynamic Mechanic Analysis (DMA). Additionally, Differential Scanning Calorimetry to determine the crystalline content of the different materials comes in support of the DMA results. Hence, this work has been designed as an exploratory study for incoming works wherein recovered carbon fibers (rSCF) will be evaluated as reinforcement of thermoplastic composites. Consequently, we studied two different polypropylene‐based composites with extreme amounts, 15% and 40% w/w, of a commercial sized SCF. Notwithstanding, just to notice that the main relaxation processes associated to the iPP matrix in the pristine composites appear sharply affected by the SCF amount, influencing also the crystalline content of the iPP matrix. The glass transition region of the iPP matrix shows significant variations well correlated with both the processing history of both the pristine iPP and the composites, and evidences the efficiency of the interfacial modifier (aPP‐SA/SA) revealed as a good candidate for improving the performance in PP/rSCF composites. POLYM. ENG. SCI., 57:731–738, 2017. © 2017 Society of Plastics Engineers